To achieve a high degree of automation at plants, factories, and such like, it is conventional to construct a distributed control system (DCS), in which devices known as field devices such as measuring devices and manipulating devices, and a control device for controlling them, are connected via a communication means. While most of the communication systems that form the foundation of such distributed control systems use wire communication, recently, some are being realized using wireless communication compliant with wireless communication standards for industrial automation, such as ISA100.11a and WirelessHART (Registered Trademark).
ISA100.11a is a wireless communication standard for industrial automation established by the International Society of Automation (ISA). WirelessHART (Registered Trademark) is a wireless communication standard established by the US Highway Addressable Remote Transducer (HART) Communications Foundation. Communication systems compliant with these wireless communication standards use time division multiple access (TDMA) as a media access control method, and provide a management apparatus known as a system manager (or a network manager) for managing the communication resources such as channels and timeslots in the TDMA.
This communication system is characterized in that, since the management apparatus mentioned above manages the communication resources, multi-hop connection is possible in addition to single-hop connection. In a single-hop connection, a wireless device (e.g. a field device capable of wireless communication) and a wireless relay device (e.g. a backbone router or a wireless access point device) are connected directly. In a multi-hop connection, the wireless device is connected to the wireless relay device via another wireless device.
The communication system described above is characterized in that connection information managed by the management apparatus (information for connecting a new wireless device to the wireless network) is supplied as advertisements from an advertisement router, thereby making it easy to connect a new wireless device to the wireless network. The non-patent document 1 discloses a method of managing communication resources in ISA100.11a.